Augmented ingestion of carbon monoxide and sulfur oxides by occupants of vehicles while idling in drive-up facility lines

Abstract

In general, for a line-up of automobiles waiting for a period of time at a drive-up facility, the idling engine emissions are expelled in a rearward direction and tend to envelope the vehicles at the end portion of the queue. Factors that affect these highly localized pollutant accumulation episodes include local meteorological conditions (low altitude inversions, winds and temperatures), number, age and tune-up condition of the cars, exhaust pipe location, interior air handling equipment, vehicle separation distances and natural or artificial barriers that form troughs or partial enclosures in which vehicular emissions can accumulate or be trapped.

In a series of typical vehicle line-ups, local CO concentrations were measured. With Santa Clara Valley background levels of 2 to 5 ppm, the 15 min average driver-area concentration levels ranged from 15 ppm to 95 ppm with short term peaks between 100 and 1000 ppm. Wide variations in concentrations can be expected if ventilating fans for heater or air conditioner units are also operating.

The exposure of humans to these concentrations of CO can result in mild headache or nausea, failure to react quickly to stimuli (like oncoming traffic) as well as setting a strain on the heart and lungs. These effects are temporary and reversible. A far more serious local air quality and health problem arises in the growing production of SO_x and sulfate compounds attributable to the legislated use of oxidizing catalytic mufflers for new car emission control and oxidation of the elemental S found in all gasoline. Using the CO levels as indicators of the accumulation of local automobile produced pollutants, when a majority of cars are equipped with catalytic converters, the anticipated adverse effects of SO_x concentrations, irritation and inflammation of healthy lung tissue of young and old people alike, as well as aggravation of preexisting conditions of lung or heart impairment, will be a most undesirable feature of drive-up facility services.

Potential reductions in the extent of this developing problem include S removal, SO_x traps and exhaust sustem redesign.